1. Field of the Invention
This invention is directed to a novel insulating wall structure for a building.
2. Description of the Prior Art
Generally, in residential construction, a building has insulated walls to inhibit the flow of heat either out of the building in the winter time or into the building in the summer time. This heat insulation factor is of particular importance in these days of high fuel prices and shortages of fuel.
It has been found that as moist air flows from the warmer or hot side to the cooler or cold side of a wall structure and is not arrested at or close to the warmer surface, it could permeate to the dew point location, either within the wall cavity or on the cold surfaces of the wall, and condense into liquid water. Such undesirable situations as paint blistering, staining, siding warping and other mositure related building problems could thus result.
In order to prevent the flow of moisture through the wall, a vapor barrier is usually employed on the warmer or room side of the wall underneath the interior gypsum board and over the framing members. This warm side vapor barrier is generally a sheet with a permeance of less than one perm. It has been recommended that where an outside vapor barrier is also present, the exterior vapor barrier should be from 5 to 10 times as vapor porous as the interior skin. Many sources recommended that cold side ventilation be provided for the escape of moisture which penetrates the wall this exterior vapor barrier is less vapor porous than the interior skin.
Sometimes an additional insulating layer such as fiberboard sheathing will be placed over the outer side of the framing members underneath the exterior siding. This layer of sheathing is very porous and allows moisture to flow out from the wall cavity. However, when this permits moisture to accumulate at the concealed surface of the exterior siding, this thoroughfare of moisture can result in paint blistering, staining, siding warping, and other moisture related problems.
Some prior art recommendations include a cold side ventilation system in which a positive air flow is provided between framing members by installing a ventilating structure at both top and bottom of the wall. In this way, there is an air wash action flowing up and inside the wall cavity. This structure, which has been widely used, also causes a great loss of thermal efficiency by displacing warm moist air from the wall cavity with cold outside air introduced into the wall cavity through the lower vent structure. Under certain conditions, entry of this colder outside air could also cause instances of moisture condensation and freezing in the wall structure.